Wireless communication terminal apparatus, wireless communication base station apparatus and signal spreading method

ABSTRACT

A wireless communication terminal apparatus wherein CoMP communication can normally be performed without increasing the overhead of an upstream line control channel. In this apparatus, a spreading unit ( 214 ) primarily spreads a response signal by use of a ZAC sequence established by a control unit ( 209 ). A spreading unit ( 217 ) secondarily spreads the response signal, to which CP has been added, by use of a block-wise spread code sequence established by the control unit ( 209 ). The control unit ( 209 ) controls, in accordance with sequence numbers and a hopping pattern established therein, the circular shift amount of the ZAC sequence to be used for the primary spread in the spreading unit ( 214 ) and the block-wise spread code sequence to be used for the secondary spread in the spreading unit ( 217 ). The hopping pattern established in the control unit ( 209 ) is a hopping pattern common to a plurality of base stations that CoMP-receive the response signal.

TECHNICAL FIELD

The present invention relates to a radio communication terminalapparatus, radio communication base station apparatus, and responsesignal spreading method.

BACKGROUND ART

In 3GPP LTE, SC-TDMA (Single-Carrier Frequency Division Multiple Access)is employed as an uplink communication method (see Non-patent Literature1). In 3GPP LTE, a radio communication base station apparatus(hereinafter simply referred to as “base station”) allocates resourcesfor uplink data to a radio communication terminal apparatus (hereinaftersimply referred to as “terminal”) through a physical channel (forexample, PDCCH (Physical Downlink Control Channel)).

Also, in 3GPP LTE, HARQ (Hybrid Automatic Repeat reQuest) is applied todownlink data from a base station to a terminal. Thus, a terminal feedsback to a base station a response signal showing an error detectionresult of downlink data. A terminal performs a CRC (Cyclic RedundancyCheck) check for downlink data, feed backs ACK (Acknowledgment) if theresult of CRC is OK (no error), and feed backs NACK (NegativeAcknowledgment) if the result of CRC is NG (error present), as aresponse signal towards a base station. A terminal transmits thisresponse signal (that is, an ACK/NACK signal) using, for example, anuplink control channel such as a PUCCH (Physical Uplink ControlChannel), to a base station.

FIG. 1 shows a resource arrangement of a PUCCH in 3GPP LTE. A PUSCH(Physical Uplink Shared Channel) shown in FIG. 1 is a channel used for aterminal to transmit uplink data, and is used when a terminal transmitsuplink data. As shown in FIG. 1, a PUCCH is placed for both ends of asystem band, that is, resource blocks (RB: Resource Block, or PRB:Physical RB) on both ends of a system band. The PUCCH placed for bothends of a system band switches between slots. That is to say a frequencyhopping is performed per slot.

As shown in FIG. 2, studies are underway to code-multiplex multipleresponse signals from multiple terminals by spreading with a ZAC (ZeroAuto Correlation) sequence and a Walsh sequence (see Non-patentLiterature 2). In FIG. 2, [W₀, W₁, W₂, W₃] represents a Walsh sequenceof a sequence length of 4. As shown in FIG. 2, in a terminal, a responsesignal of ACK or NACK is subjected to the first spreading using asequence which has a characteristic becoming a ZAC sequence (sequencelength 12) in the frequency domain and in the time domain at first.Next, response signals after the first spreading are associated witheach W₀-W₃ and are subjected to an IFFT (Inverse Fast FourierTransform). A response signal spread in the frequency domain istransformed by this IFFT into a ZAC sequence which has a sequence lengthof 12 in the time domain. Also, a signal after the IFFT is furthersubjected to second spreading using a Walsh sequence (sequence length4). Thus, one response signal is placed for four SC-FDMA symbols S₀-S₃.This applies to other terminals alike, and a response signal is spreadusing a ZAC sequence and a Walsh sequence. However, different terminalsuse ZAC sequences of different cyclic shift amounts in the time domainor use different Walsh sequences. Since the sequence length of a ZACsequence in the time domain is 12 here, twelve ZAC sequences generatedfrom the same ZAC sequence and having cyclic shift amounts 0-11, can beused. Since the sequence length of a Walsh sequence is 4, four mutuallydifferent Walsh sequences can be used. Thus, in an ideal communicationenvironment, response signals from maximum 48 (12×4) terminals can becode-multiplexed.

As shown in FIG. 2, studies are underway to code-multiplex multiple thereference signals (a pilot signal) from multiple terminals (seeNon-patent Literature 2). As shown in FIG. 2, to generate a referencesignal of three symbols R₀, R₁ and R₂ from a ZAC sequence (sequencelength 12), first, the ZAC sequence is subjected to an IFFT inassociation with an orthogonal sequence of a sequence length of 3, [F₀,F₁, F₂], such as a Fourier sequence. By this IFFT, a ZAC sequence whichis a sequence length of 12 in the time domain is acquired. Then, asignal after the IFFT is spread using an orthogonal sequence [F₀, F₁,F₂]. Thus, one reference signal (ZAC sequence) is allocated to threeSC-FDMA symbols, R₀, R₁, and R₂. This applies to other terminals alike,and one reference signal (a ZAC sequence) is allocated to three SC-FDMAsymbols, R₀, R₁, and R₂. However, different terminals use ZAC sequencesof different cyclic shift amounts in the time domain or use differentorthogonal sequences. Since the sequence length of a ZAC sequence in thetime domain is 12 here, twelve ZAC sequences generated from the same ZACsequence and having cyclic shift amounts 0-11, can be used. Since thesequence length of an orthogonal sequence is 3, three mutually differentorthogonal sequences are used. Thus, in an ideal communicationenvironment, reference signals from maximum 36 (12×3) terminals can becode-multiplexed.

As shown in FIG. 2, seven symbols of S₀, S₁, R₀, R₁, R₂, S₂, and S₃ formone slot.

Here, the cross-correlation between ZAC sequences of different cyclicshift amounts which are generated from the same ZAC sequence, becomesalmost zero. Thus, in an ideal communication environment, multipleresponse signals, which are spread and code-multiplexed using ZACsequences (cyclic shift amount 0-11) of different cyclic shift amounts,can be separated in the time domain nearly without inter symbolinterference by a correlation processing in a base station.

However, because of influences such as a misalignment of transmittingtiming at a terminal and a delayed wave caused by multipath, multipleresponse signals from multiple terminals may not arrive at to a basestation at the same time. For example, if transmission timing of aresponse signal spread using the ZAC sequence of cyclic shift amount 0is later than the correct timing, the correlation peak of the ZACsequence of cyclic shift amount 0 may appear in a detecting window for aZAC sequence of cyclic shift amount 1. If a response signal which hasbeen spread using the ZAC sequence of cyclic shift amount 0 has adelayed wave, an interference leakage due to the delayed wave may appearin a detecting window for a ZAC sequence of cyclic shift amount 1. Thus,in these cases, a ZAC sequence of cyclic shift amount 1 suffersinterference from a ZAC sequence of cyclic shift amount 0. On the otherhand, if transmission timing of a response signal spread using the ZACsequence of cyclic shift amount 0 is earlier than the correct timing,the correlation peak of the ZAC sequence of cyclic shift amount 1 mayappear in a detecting window for a ZAC sequence of cyclic shift amount0. Thus, in this case, a ZAC sequence of cyclic shift amount 0 suffersinterference from a ZAC sequence of cyclic shift amount 1. Thus, in thiscase, the separation characteristics of a response signal spread usingthe ZAC sequence of cyclic shift amount 0 and a response signal spreadby a ZAC sequence of cyclic shift amount 1 are degraded. Thus, if ZACsequences having mutually adjacent cyclic shift amounts are used, theseparation characteristic of a response signal may be degraded.

Thus, previously, if multiple response signals are code-multiplexed byZAC sequence spreading, a cyclic shift interval (a gap between cyclicshift amounts) of such a scale that does not produce inter symbolinterference between ZAC sequences, is provided between ZAC sequences.For example, if the cyclic shift interval between ZAC sequences isdefined as 2, between twelve sequences which have a sequence length of12 and which have cyclic shift amounts 0-11, only six ZAC sequences ofcyclic shift amounts 0, 2, 4, 6, 8, and 10, or of cyclic shift amounts1, 3, 5, 7, 9, and 11, are used for the first spreading of a responsesignal. Thus, if a Walsh sequence which has a sequence length of 4 isused for second spreading of a response signal, response signals frommaximum 24 (6×4) terminals can be code-multiplexed.

However, as shown in FIG. 2, the sequence length of an orthogonalsequence used to spread a reference signal is 3, so that only threemutually different orthogonal sequences can be used to spread areference signal. Thus, if multiple response signals are separated usinga reference signal shown in FIG. 2, only response signals from maximum18 (6×3) terminals can be code-multiplexed. Thus, three out of fourWalsh sequences which have a sequence length of 4 are enough, so thatone Walsh sequence remains unused.

Also, as a PUCCH to be used to transmit to the above mentioned eighteenresponse signals, studies are underway to define eighteen PUCCHs (ACK#1-ACK #18 shown in FIG. 3) shown in FIG. 3. in FIG. 3, the horizontalaxis represents the cyclic shift amount, and the vertical axisrepresents the sequence numbers of orthogonal code sequences (sequencenumbers of a Walsh sequence or a Fourier sequence).

To reduce interference from other cells in PUCCH, a technology calledcyclic shift hopping is discussed (see Non-patent Literature 3). Cyclicshift hopping refers to a technology of cyclically shifting, forexample, the eighteen resources (ACK #1-ACK #18) shown in FIG. 3, inSC-FDMA symbol units (in FIG. 4, symbol 0, 2, . . . , n), using thecell-specific cyclic shift hopping pattern as shown in FIG. 4,maintaining their correlation relationships on a cyclic shift axis andon an orthogonal code axis. As shown in FIG. 4, although the amount ofcyclic shift which resources to which a certain response signal isallocated use changes per SC-FDMA symbol, the relative relationships ofresources (cyclic shift amount and orthogonal code) under the same timeand the same frequency are maintained in a cell, so that these eighteenresources are orthogonal to each other. This can randomize thecombination of response signals to suffer severe interference from othercells, so that no longer do some terminals alone continue sufferingsevere interference from other cells. Generally, different ZAC sequencesare allocated to different cells, so that the ZAC sequence differencesbetween cells contribute to randomization of interference.

Meanwhile, in a PUCCH of 3GPP LTE the above mentioned response signal(an ACK/NACK signal) and also a CQI (Channel Quality Indicator) signalare multiplexed. Although a response signal is an one-symbol ofinformation (information indicated by using one symbol) as mentionedabove, a CQI signal is a five-symbol of information (informationindicated by using five symbols). As shown in FIG. 5, a terminal spreadsa CQI signal using a ZAC sequence which has a sequence length of 12, andperforms an IFFT on the spread CQI signal, and transmits the CQI signal.By this means, a Walsh sequence is not applied for a CQI signal, sothat, in a base station, a Walsh sequence cannot be used to separate aresponse signal and a CQI signal. Therefore, using a ZAC sequence, abase station despreads a response signal and CQI signal which have beenspread by the ZAC sequences corresponding to different cyclic shifts, sothat a base station can separate a response signal and CQI signal nearlywithout inter symbol interference.

Like response signals, studies are underway to apply cyclic shifthopping to CQI signals in SC-FDMA units, using cell specific cyclicshift hopping pattern to randomize inter-cell interference. As shown inFIG. 6, although the amount of cyclic, shift which resources to which acertain CQI signal is allocated use changes per SC-FDMA symbol, therelative relationships of the amount of cyclic shift under the same timeand the same frequency are maintained. Like response signals, differentZAC sequences are allocated to different cells of CQI signals, so thatthe ZAC sequence differences between cells contribute to randomizationof interference.

In 3GPP LTE, the cyclic shift hopping patterns shown in FIG. 4 and FIG.6 are associated with the cell IDs of base stations one by one.

Also, the standardization of LTE-advanced (hereinafter referred to as“LTE+”) has been started to realize much faster communication than 3GPPLTE. In LTE+, to improve average throughput and improve throughput of aterminal located near a cell edge, CoMP transmission/reception(Coordinated Multipoint Transmission/Reception) where multiple basestations cooperate to transmit and receive signals and coordinateinter-cell interference, is discussed.

CITATION LIST Non-Patent Literature

NPL 1

-   3GPP TS 36.211 V8.4.0, “Physical Channels and Modulation (Release    8),” September 2008    NPL 2-   Multiplexing capability of CQIs and ACK/NACKs form different UEs    (ftp://ftp.3gpp.org/TSG_RAN/WG1_RL1/TSGR1_49/Docs/R1-072315.zip)    NPL 3-   Randomization of intra-cell interference in PUCCH    (ftp://ftp.3gpp.org/TSG_RAN/WG1_R1/TSGR1_50/Does/R1-073412.zip)

SUMMARY OF INVENTION Technical Problem

For example, FIG. 7 shows a case where multiple base stations receive anuplink response signal from one terminal (that is, CoMP reception). InFIG. 7, a base station (serving eNB) to which a certain terminal (UE 1)belongs transmits downlink data to UE 1. Also, UE 1 transmits a responsesignal (desired ACK/NACK shown in FIG. 7) to downlink data. Then, asshown in FIG. 7, three base stations—the serving eNB and other basestations (neighbor eNB 1 and neighbor eNB 2) —receive the responsesignal from UE 1 in CoMP reception. Here, a group of multiple basestations to receive response signals from a terminal by CoMP receptionis referred to as a CoMP group. The three base stations shown in FIG. 7exchange through backhaul, analog information (soft bit information) ofthe response signals from UE 1 which the base station each have receivedfrom UE 1. The serving eNB combines analog information of the responsesignal which has been received in the three base stations by, forexample, MRC (Maximum Ratio Combining), and decodes the response signal.Also, the serving eNB performs retransmit control of downlink data to UE1, based on a decoded response signal.

Also, FIG. 8 shows a case where multiple base stations transmit downlinkdata (reference signal) to one terminal (that is, CoMP transmission), aterminal transmits a CQI signal generated by using the reference signaltransmitted from the multiple base stations in CoMP transmission, andthe multiple base stations receive the CQI signal from the terminal inCoMP reception. In FIG. 8, three base stations which join the same CoMPgroup (serving eNB, neighbor eNB 1, and neighbor eNB 2) transmit thesame downlink data (reference signal) to UE 1 belonging to the servingeNB in CoMP transmission. UE 1 estimates downlink quality between UE 1and each base station using a received reference signal, and transmitsCQI information showing each downlink quality to each base station.However, UE 1 transmits CQI information for three base stations alltogether in one CQI signal (a desired CQI shown in FIG. 8). The threebase stations shown in FIG. 8 each receive a CQI signal from UE 1 inCoMP reception. Here, as in FIG. 7, three base stations exchange throughbackhaul analog information (soft bit information) of the CQI signalswhich the base station each have received. The serving eNB combinesanalog information of the CQI signal which has been received in thethree base stations by, for example, MRC (Maximum Ratio Combining), anddecodes the CQI signal. Also, the serving eNB controls MCS (Modulationand Coding Scheme) of downlink data to transmit from each base station,or a spatial multiplexing, based on a decoded CQI signal, that is, thedownlink quality between UE 1 and each base station.

Here, in FIG. 7 and FIG. 8, the three base stations to receive a controlsignal from UE 1 (a response signal or a CQI signal) in CoMP reception,also receive a control signal (a response signal or a CQI signal) fromUE 2, which uses eNB 2 as the serving eNB, in CoMP reception. Thus, inFIG. 7 and FIG. 8, three base stations join the same CoMP group,receives control signals from two terminals in CoMP reception.

However, as mentioned above, to randomize inter-signal interferencebetween control signals transmitted from terminals belonging torespective cells, ZAC sequences that vary per cell and cell-specifichopping patterns are used. For example, in FIG. 7 and FIG. 8, UE 1belonging to the serving eNB and UE 2 belonging to the neighbor eNB 2use mutually different ZAC sequences and hopping patterns. Thus, thecontrol signals from UE 1 (a response signal and a CQI signal) and thecontrol signals from UE 2 (a response signal and a CQI signal) are notorthogonal and interfere with each other.

Thus, for example, a response signal from UE 1 shown in FIG. 7 istransmitted using a ZAC sequence and hopping pattern that are specificto a serving eNB, and a response signal from UE 2 is transmitted using aZAC sequence and hopping pattern that are specific to a neighbor eNB 2.Therefore, in the neighbor eNB 2, a response signal from UE 1 and aresponse signal from UE 2 are not orthogonal to each other and interferewith each other. Thus, this raises a problem that a response signal fromUE 1 and a response signal from UE 2 interfere with each other and causedeterioration of CoMP quality.

Even when multiple terminals use the same CoMP group, if the serving eNBis differed per each terminal, the above mentioned problem can be solvedby separating time and frequency resources to use as a control channel(for example, PUCCH). However, in this case, the overhead of an uplinkcontrol channel used for CoMP communication will increase.

It is therefore an object of the present invention to provide aterminal, a base station, and a signal spreading method which allowsefficient CoMP communication without increasing an overhead of an uplinkcontrol channel.

Solution to Problem

The terminal of the present invention employs a configuration having: afirst spreading section that performs first spreading of a signal usingone of a plurality of first sequences that can be separated from eachother; and a control section that controls a first sequence to be usedin the first sequence section according to a hopping pattern for aplurality of channels that are defined by the plurality of firstsequences, where the hopping pattern is a common hopping pattern betweena plurality of radio communication base station apparatuses that receivethe signal in coordinated multipoint reception.

The base station of the present invention employs a configurationhaving: a correlation processing section that calculates a correlationvalue between a signal from a radio communication terminal apparatus anda first sequence used for first spreading in the radio communicationterminal apparatus, using a hopping pattern for a plurality of channelsdefined by a plurality of first sequence that can be separated from eachother; and a combining section that combines the correlation value and acorrelation value of the signal received by other radio communicationbase station apparatus which receives the signal in coordinatedmultipoint reception, where the hopping pattern is a common hoppingpattern between the plurality of radio communication terminalapparatuses that receive the signal in coordinated multipoint reception.

The signal spreading method of the present invention includes: a firstspreading step of performing first spreading for a signal using one of aplurality of first sequences that can be separated from each other; anda control step of controlling a first sequence to be used in the firstspreading section according to a hopping pattern for a plurality ofchannels that are defined by the plurality of first sequences, where thehopping pattern is a common hopping pattern between a plurality of radiocommunication base station apparatuses that receive the signal incoordinated multipoint reception.

Advantageous Effects of Invention

According to the present invention, without increasing an overhead ofuplink control channel, CoMP communication can be performed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a resource arrangement of PUCCH (prior art);

FIG. 2 shows the method of spreading a response signal and a referencesignal (prior art);

FIG. 3 shows a definition of a response signal (prior art);

FIG. 4 shows a hopping pattern of a response signal (prior art);

FIG. 5 shows the method to spread a CQI signal and a reference signal(prior art);

FIG. 6 shows a hopping pattern of a CQI signal (prior art);

FIG. 7 shows CoMP reception of a response signal (prior art);

FIG. 8 shows CoMP transmission of a reference signal and CoMP receptionof a CQI signal (prior art);

FIG. 9 is a block diagram showing a configuration of a base stationaccording to embodiment 1 of the present invention;

FIG. 10 is a block diagram showing a configuration of a terminalaccording to embodiment 1 of the present invention;

FIG. 11A shows a CoMP group according to embodiment 1 of the presentinvention;

FIG. 11B shows a response signal resource according to embodiment 1 ofthe present invention;

FIG. 12 is a block diagram showing a configuration of a base stationaccording to embodiment 2 of the present invention;

FIG. 13 is a block diagram showing a configuration of a terminalaccording to embodiment 2 of the present invention;

FIG. 14A shows a CoMP group according to embodiment 2 of the presentinvention; and

FIG. 14B shows a CQI signal resource according to embodiment 2 of thepresent invention.

DESCRIPTION OF EMBODIMENTS

Now, embodiments of the present invention will be explained in detailwith reference to the accompanying drawings.

(Embodiment 1)

FIG. 9 shows a configuration of base station 100 according to thepresent embodiment, and FIG. 10 shows a configuration of terminal 200according to the present embodiment.

Here, to avoid complicated explanation, FIG. 9 shows only componentspertaining to a transmission of downlink data and a reception in anuplink of the response signal associated with the downlink data, towhich the present invention is closely related, and illustration anddescription of parts or components pertaining to uplink data receptionare omitted. In the same way, FIG. 10 shows only components pertainingto a reception of downlink data and a transmission in an uplink of theresponse signal associated with the downlink data, to which the presentinvention is closely related, and illustration and description of partsor components pertaining to uplink data reception are omitted.

Then, in the following explanation, a case will be explained where a ZACsequence is used for the first spreading and a blockwise spreading codesequence is used for second spreading. However, for the first spreading,besides ZAC sequences, it is equally possible to use sequences that havemutually different amounts of cyclic shift and are separable. Forexample, a PN sequence, such as a GCL (Generalized Chirp like) sequence,a CAZAC (Constant Amplitude Zero Auto Correlation) sequence, a ZC(Zadoff-Chu) sequence, an M sequence, and an orthogonal Gold codesequence, or a sequence which is generated randomly by a computer andwhich has steep auto-correlation characteristics, may be used for thefirst spreading. Also, for second spreading, any sequences may be usedas blockwise spreading code sequences as long as the sequences aremutually orthogonal or the sequences can be identified as nearlymutually orthogonal. For example, a Walsh sequence or Fourier sequencemay be used for second spreading as a blockwise spreading code sequence.

Also, in the following explanation, the response signal resources (forexample, PUCCH or PRB) are determined by the cyclic shift amount of ZACsequence and the sequence number of a blockwise spreading code sequence.

Also, in the following explanation, IDs (hereinafter referred to as“special IDs”) that are set on a per CoMP group basis are associatedwith time and frequency resources (for example, PRBs) for uplinkresponse signal transmission. Special IDs are adjusted in advancebetween multiple base stations joining the same CoMP group. Also, whencommunicating with terminals, each base station reports to each terminalwhether or not a response signal from that terminal is to be received inCoMP reception. Each base station also reports the special ID associatedwith the CoMP group that the base station joins, to a terminal thattransmits a response signal to be received in CoMP reception. Each basestation also reports its cell ID to a terminal belonging to the basestation. Here, the bit number of special ID and the bit number of cellID is equal.

Base station 100 shown in FIG. 9 reports to each terminal in advanceinformation showing whether or not a response signal which each terminaltransmits is to be received in CoMP reception by multiple base stationsincluding base station 100, information showing the cell ID of basestation 100, information showing a resource (for example, PRB) for whicha response signal which each terminal transmits, is allocated, andinformation showing the special ID associated with a CoMP group to whichthe base station 100 belongs (not shown).

Also, in base station 100 shown FIG. 9, the resource allocation resultof downlink data is input to control information generating section 101and mapping section 104. Also, a coding rate of each terminal of controlinformation to report the resource allocation result of downlink data isinput as coding rate information for control information generatingsection 101 and coding section 102.

Control information generating section 101 generates control informationfor each terminal to report the resource allocation result of downlinkdata, and outputs this information to coding section 102. Controlinformation for each terminal includes terminal ID information showingwhich terminal the control information is addressed to. For example, aCRC bit that is masked by an ID number of a terminal to which controlinformation is sent is included in the control information as terminalID information.

According to coding rate information received as input, coding section102 encodes the control information for each terminal and outputs thecontrol information to modulating section 103.

Modulating section 103 modulates the encoded control information andoutputs the result to mapping section 104.

On the other hand, coding section 105 encodes transmission data for eachterminal (downlink data) and outputs the transmission data toretransmission control section 106.

Upon the initial transmission, retransmission control section 106 holdsencoded transmission data for each terminal and outputs the transmissiondata to modulating section 107. Retransmission control section 106 holdstransmission data until ACK from each terminal is input fromdetermination section 118. Also, if NACK from each terminal is inputfrom determination section 118, that is, upon retransmission,retransmission control section 106 outputs transmission data associatedwith that NACK to modulating section 107.

Modulating section 107 modulates encoded transmission data input fromretransmission control section 106 and outputs the result to mappingsection 104.

When transmitting control information, mapping section 104 maps controlinformation input from modulating section 103 to physical resources(time and frequency resources) according to the resource allocationresult input from control information generating section 101, andoutputs the control information to IFFT section 108.

On the other hand, when transmitting downlink data, mapping section 104maps transmission data for each terminal to physical resources accordingto the resource allocation result and outputs the transmission data toIFFT section 108. Thus, mapping section 104 maps transmission data foreach terminal to either one of a plurality of subcarriers that forms anOFDM symbol according to the resource allocation result.

IFFT section 108 performs an IFFT on a plurality of subcarriers to whichcontrol information or transmission data is mapped, generates an OFDMsymbol, and outputs the symbol to CP (Cyclic Prefix) adding section 109.

CP adding section 109 attaches a signal that is the same as the tail endpart of an OFDM symbol to the beginning of that OFDM symbol as a CP.

Radio transmitting section 110 performs a transmission processing, suchas D/A conversion, amplification, and up-conversion for the OFDM symbolwith a CP and transmits the symbol to terminal 200 (FIG. 10) throughantenna 111.

On the other hand, radio receiving section 112 receives a responsesignal or a reference signal transmitted from terminal 200 throughantenna 111, and performs receiving processing, such as down-conversionand A/D conversion for the response signal or reference signal.

CP removing section 113 removes the CP added to a response signal orreference signal after the receiving processing.

Despreading section 114 despreads a response signal using the blockwisespreading code sequence used for second spreading in terminal 200, andoutputs the despread response signal to correlation processing section116. In the same way, despreading section 114 despreads a responsesignal using the orthogonal sequence used to spread a reference signalin terminal 200, and outputs the despread reference signal tocorrelation processing section 116.

Generating section 115 decides whether a response signal to betransmitted from terminal 200 is a response signal to be received inCoMP reception by multiple base stations including base station 100, oris a response signal to be received only by base station 100, andgenerates a ZAC sequence and frequency hopping pattern based on thedecision. For example, if a response signal is to be received in CoMPreception, generating section 115 generates a ZAC sequence and hoppingpattern associated with the special ID set for the CoMP group which basestation 100 joins. Here, special IDs and hopping patterns set for CoMPgroups are associated on a one-by-one basis. That is, the hoppingpattern to use for a response signal to be received in CoMP reception isa hopping pattern that is common between a plurality of base stationsthat receive the response signal in CoMP reception, that is, a commonhopping pattern for a plurality of base stations (cells) that belong tothe same CoMP group. On the other hand, if a response signal is receivedonly by base station 100, generating section 115 generates a ZACsequence and hopping pattern associated with the cell ID of base station100. Generating section 115 outputs the generated ZAC sequence andhopping pattern to correlation processing section 116.

Using the ZAC sequence and hopping pattern input from generating section115, correlation processing section 116 calculates the correlation valuebetween a despread response signal, a despread reference signal, and theZAC sequence used for the first spreading in terminal 200. Then,correlation processing section 116 outputs the calculated correlationvalue to determination section 118 and CoMP control section 117. Here,the cyclic shift amount to use for cyclic shift hopping in eachterminal, differs in SC-TDMA units. For this reason, according to thehopping pattern input from generating section 115, correlationprocessing section 116 extracts a response signal and a reference signalfrom terminals, from correlation windows which differs per SC-FDMAsymbol.

When base station 100 operates as the serving eNB for a terminal havingtransmitted a response signal (that is, when a terminal which hastransmitted a response signal belongs to base station 100), CoMP controlsection 117 outputs information transmitted from other base stationsbelonging to the same CoMP group as base station 100 through backhaul(that is, the correlation value of a response signal calculated by otherbase station), to determination section 118. On the other hand, if basestation 100 is not the serving eNB for the terminal which transmitted aresponse signal (that is, the terminal having transmitted a responsesignal belongs to another cell), CoMP control section 117 transmitsthrough backhaul the correlation value input from correlation processingsection 116 (the correlation value of a response signal which iscalculated by base station 100), to other base station belonging to thesame CoMP group as base station 100.

Determination section 118 combines the correlation value input fromcorrelation processing section 116 and the correlation value input fromCoMP control section 117 (the correlation value of response signalsreceived by other base stations belonging to the same CoMP group as basestation 100) by, for example MRC. Then, determination section 118, basedon the combination result, decides whether response signals of terminalsare ACK or NACK by synchronous detection using the correlation value ofa reference signal. Then, determination section 118 outputs ACK or NACKfor each terminal to retransmission control section 106.

On the other hand, in terminal 200 shown in FIG. 10, radio receivingsection 202 receives through antenna 201 an OFDM symbol transmitted frombase station 100, and performs receiving processing, such asdown-conversion and A/D conversion for an OFDM symbol.

CP removing section 203 removes CP added to the OFDM symbol after thereceiving processing.

FFT (Fast Fourier Transform) section 204 performs an FFT on the OFDMsymbol, receives the control information which is mapped to a pluralityof subcarriers, or the downlink data, and outputs those to extractingsection 205.

Coding rate information showing the coding rate of control informationis input to extracting section 205 and decoding section 207.

When receiving the control information, extracting section 205 extractsthe control information from a plurality of subcarriers according tocoding rate information received as input, and outputs the controlinformation to demodulating section 206.

Demodulating section 206 demodulates the control information and outputsthe control information to decoding section 207.

Decoding section 207 decodes the control information according to codingrate information received as input and outputs the control informationto determination section 208.

On the other hand, when receiving downlink data, extracting section 205extracts downlink data which is transmitted to terminal 200 from aplurality of subcarriers according to the resource allocation resultinput from determination section 208, and outputs the downlink data todemodulating section 210. This downlink data is demodulated indemodulating section 210, decoded in decoding section 211, and input toCRC section 212.

CRC section 212 performs the error detection using a CRC for the decodeddownlink data, if the result of CRC is OK (no error), CRC section 212generates ACK, if the result of CRC is NG (error present), CRC section212 generates NACK as a response signal, and outputs the generatedresponse signal to modulating section 213. Also, if the result of CRC isOK (no error), CRC section 212 outputs the decoded downlink data asreceived data.

Determination section 208 performs blind detection to decide whether ornot control information input from decoding section 207 is controlinformation for terminal 200. For example, if the result of CRC is OK(no error) by demasking a CRC bit with the ID number of terminal 200,determination section 208 determines that the control information is thecontrol information to terminal 200. Then, determination section 208outputs to extracting section 205 the control information to terminal200, that is, the resource allocation result of downlink data toterminal 200.

Also, determination section 208 determines the resource (for example,PUCCH) to be used to transmit a response signal from terminal 200, fromthe physical resources (time and frequency resources) associated withthe subcarrier to which control information to terminal 200 is mapped,and outputs the decision to control section 209.

Control section 209 holds information that is reported in advance frombase station 100 to which terminal 200 belongs and that shows whether ornot a response signal transmitted from terminal 200 is to be received bymultiple base stations in CoMP reception, information that shows thecell ID of the base station to which terminal 200 belongs, informationthat shows a resource (for example, PRB (Physical Resource Block)) towhich a response signal, transmitted by terminal 200, is allocated, andinformation that shows the special ID associated with the CoMP groupwhen a response signal from terminal 200 is received in CoMP reception.

If a response signal transmitted by terminal 200 is to be received inCoMP reception, control section 209 sets a sequence number and hoppingpattern, based on the special ID associated with time and frequencyresources used to transmit a response signal (that is, the special IDset for the CoMP group to which multiple base stations belong, multiplebase stations including base station 100 to which terminal 200 belongs).Here, the hopping pattern to use if a response signal is to be receivedin CoMP reception is a hopping pattern that is common between aplurality of base stations which receive a response signal in CoMPreception, that is, a plurality of base stations which belong to thesame CoMP group. On the other hand, if a response signal transmittedfrom terminal 200 is not to be received in CoMP reception, controlsection 209 sets a sequence number and hopping pattern based on the cellID reported from base station 100. Also, according to the set sequencenumber and hopping pattern, control section 209 controls a cyclic shiftamount of a ZAC sequence to use for the first spreading in spreadingsection 214, and a blockwise spreading code sequence to use for secondspreading in spreading section 217. The details of a sequence control atcontrol section 209 will be described later. Also, control section 209outputs a ZAC sequence as a reference signal to IFFT section 220.

Modulating section 213 modulates a response signal input from CRCsection 212 and outputs the result to spreading section 214.

Spreading section 214 performs the first spreading on a response signalusing a ZAC sequence set by control section 209, and outputs a responsesignal after the first spreading to IFFT section 215. That is, spreadingsection 214 performs the first spreading of a response signal accordingto a sequence and hopping pattern specified from control section 209.Here, since the cyclic shift amount to use for cyclic shift hoppingdiffers per SC-FDMA unit, spreading section 214 performs the firstspreading of response signals using different cyclic shift amounts inSC-FDMA symbol units.

IFFT section 215 performs an IFFT to the response signal after the firstspreading, and outputs the response signal after the IFFT to CP addingsection 216.

CP adding section 216 attaches a signal that is the same as the tail endpart of a response signal after an IFFT to the beginning of thatresponse signal as a CP.

Spreading section 217 performs second spreading for the response signalwith a CP using a blockwise spreading code sequence set by controlsection 209, and outputs the response signal after second spreading tomultiplexing section 218. That is, spreading section 217 performs secondspreading for a response signal after the first spreading using ablockwise spreading code sequence associated with the resource selectedat control section 209.

IFFT section 220 performs an IFFT on a reference signal and outputs thereference signal after the IFFT to CP adding section 221.

CP adding section 221 attaches a signal that is the same as the tail endpart of an reference signal after an IFFT to the beginning of thatreference signal as a CP.

Spreading section 222 spreads the reference signal with a CP using theorthogonal sequence set in advance, and outputs the spread referencesignal to multiplexing section 218.

Multiplexing section 218 time-multiplexes a response signal after secondspreading and a spread reference signal into one slot, and outputs theresults to radio transmitting section 219.

Radio transmitting section 219 performs transmission processing such asD/A conversion, amplification, and up-conversion to a response signalafter second spreading and a spread reference signal and transmitsthrough antenna 201 to base station 100 (FIG. 9).

The details of a sequence control and hopping pattern control at controlsection 209 will be described in the following.

In the following description, eNB 1-eNB 5 shown in FIG. 11A each havethe configuration of base station 100 shown in FIG. 9, and UE 1-UE 3each have the configuration of terminal 200 shown in FIG. 10. Also, eachUE receives downlink data from an eNB to which each UE belongs, andtransmits a response signal to that downlink data. As shown in FIG. 11A,among eNB 1-eNB 5, eNB 1-eNB 3 join CoMP group A, and eNB 1, eNB 4, andeNB 5 join CoMP group B. As shown in FIG. 11A, UE 1 belongs to eNB 1, UE2 belongs to eNB 3, and UE 3 belongs to eNB 4.

Also, uplink resources for transmitting a response signal (for example,a plurality of PUCCHs shown in FIG. 1) is represented as a plurality ofPRBs (PRB for a response signal), as shown in FIG. 11B. As shown in FIG.11B, among a plurality of PRBs, some of these PRBs are set on a per CoMPgroup basis. Also, the special IDs of CoMP groups are associated withPRBs corresponding to CoMP groups.

Thus, eNB 1-eNB 3 joining CoMP group A shown in FIG. 11A have a specialID of CoMP group A, and eNB 1, eNB 4, and eNB 5 joining CoMP group Bhave a special ID of CoMP group B. A special ID of CoMP group A and PRBfor a response signal of CoMP group A shown in FIG. 11B are reported toUE 2 in CoMP group A. A special ID of CoMP group B and PRB for aresponse signal of CoMP group B shown in FIG. 11B are reported to UE 3in CoMP group B. Also, eNB 1 joins both CoMP group A and CoMP group B,and has both special IDs of CoMP group A and CoMP group B. However, oneUE does not join a plurality of CoMP groups, eNB 1 reports to UE 1 aspecial ID of any one of CoMP group A or CoMP group B. Here, UE 1belonging to eNB 1 joins CoMP group A. Thus, a special ID of CoMP groupA and PRB for a response signal of CoMP group A shown in FIG. 11B arereported to UE 1.

Thus, if control section 209 of each UE is reported that a responsesignal which that UE transmits is not to be received in CoMP reception,control section 209 of each UE calculates a spread sequence and hoppingpattern of a response signal using the cell ID of an eNB to which thatUE belongs. Specifically, in FIG. 11A, UE 1 calculates a spread sequenceand hopping pattern associated with the cell ID of eNB 1, UE 2calculates a spread sequence and hopping pattern associated with thecell ID of eNB 3, and UE 3 calculates a spread sequence and hoppingpattern associated with the cell ID of eNB 4.

On the other hand, if control section 209 of each UE is reported aresponse signal which that UP transmits is to be received in CoMPreception, control section 209 of each UE calculates a spread sequenceand hopping pattern of a response signal using the special ID of CoMPgroup which an eNB, to which that UE belongs, joins. Specifically, inFIG. 11A, UE 1 calculates a spread sequence and hopping patternassociated with the special ID of CoMP group A, UE 2 calculates a spreadsequence and hopping pattern associated with the special ID of CoMPgroup A, and UE 3 calculates a spread sequence and hopping patternassociated with the special ID of CoMP group B.

Each UE allocates a response signal spread using the spread sequence andhopping pattern controlled by control section 209 to the PRB associatedwith the special ID and transmits this response signal.

Therefore, UEs located in the same CoMP group (UE 1 and UE 2 shown inFIG. 11) spread a response signal using a spread sequence and hoppingpattern associated with the same special ID (special ID of CoMP groupA). By this means, even UE 1 and UE 2 which are located in the same CoMPgroup and which belong to mutually different eNBs, spread a responsesignal using the same spread sequence and hopping pattern. Also, aresponse signal which UE 1 transmits and a response signal which UE 2transmits are code-multiplexed with PRBs for CoMP group A shown in FIG.11B. Thus, at multiple eNBs joining the same CoMP group, responsesignals that are individually transmitted from UEs belongingrespectively the eNBs joining the same CoMP group are receivedorthogonal to each other in CoMP reception.

By this means, even if the base stations being the serving eNB variesper terminal (that is, even if each terminal belongs to a different basestation's cell), it is still possible to code-multiplex response signalsin the same PRB. Base stations joining the same CoMP group can receiveresponse signals from each terminal, which are orthogonal to each other,in CoMP reception. Thus, in each base station, each response signal canbe decoded without mutual interference.

According to the present embodiment, response signals to be received inCoMP reception by a plurality of base stations are spread using ahopping pattern which is common between a plurality of base stationsjoining the same CoMP group. Thus, each terminal can make a responsesignal to be received in CoMP reception in the same CoMP group, beorthogonal to each other, and be code-multiplexed with time andfrequency resources (PRBs) used as an uplink control channel. For thisreason, a response signal transmitted from each terminal are orthogonalto each other and does not interfere with each other, so that each basestation can effectively receive a response signal from each terminal inCoMP reception. Thus, according to the present embodiment, CoMPcommunication can be performed effectively without increasing anoverhead of uplink control channel.

Here, for example, to perform CoMP communication in an uplink controlchannel (for example, PUCCH), if a base station reports a spreadsequence and hopping pattern to use to spread a response signal (thatis, a spread sequence and hopping pattern associated with a CoMP group)to each terminal, the amount of signaling of reporting information willincrease. However, according to the present embodiment, a special ID isset for each CoMP group, so that, the only reporting information forCoMP communication which a base station has to report to a terminal isthe special ID having the same number of bits as the cell ID. Thus,according to the present embodiment, the increase of the amount ofsignaling of reporting information from a base station to a terminal canbe prevented.

Generally, a cell ID is associated with a spread sequence and hoppingpattern to be used for a response signal, and furthermore, associatedwith a set of such as a mapping of PDCCH (an interleave pattern) or a DLRS (Downlink Reference Signal) sequence. Thus, since a cell ID isassociated with both uplink and downlink parameters, changing a cell IDmight possible influence both uplink and downlink parameters andnecessitate numerous changes in the upper layer. On the other hand, withthe present embodiment, if a plurality of base stations receive aresponse signal from a terminal in CoMP reception, a special ID that isassociated only with uplink parameters (a spread sequence and hoppingpattern of a response signal), that is, an identifier unrelated todownlink parameters, is used. For this reason, according to the presentembodiment, a base station can receive a response signal in CoMPreception without affecting a downlink parameter.

Also, each terminal should only control a spread sequence and hoppingpattern based on the cell ID or special ID reported from a base station,and does not need to consider which base station the terminal transmitsa response signal to. Thus, according to the present embodiment, theterminal can control properly only by receiving information reportedfrom a base station, so that the terminal can be simplified.

The only difference between the present embodiment and 3GPP LTEoperation is the usage of a special ID to perform CoMP communication.Thus, a terminal can reuse most parts of 3GPP LTE operation. Thus,according to this embodiment, it is possible to minimize changes in theupper layer and minimize the increase of the amount of signaling ofcontrol information to the terminal.

Also, a case has been described with the present embodiment where eachterminal receives downlink data from one base station and transmits aresponse signal to that downlink data. However, in the presentinvention, each terminal may receive downlink data from a plurality ofbase stations at the same time. In other words, a plurality of basestations may transmit downlink data to one terminal in CoMPtransmission. By this means, a terminal can improve the received qualityof downlink data.

(Embodiment 2)

A case has been described with embodiment 1 where multiple base stationsreceive response signals in CoMP reception. By contrast with this, acase will be described with the present embodiment where a plurality ofbase stations join the same CoMP group, transmit in CoMP transmissiondownlink data (a reference signal) to a terminal, and receive in CoMPreception a CQI signal shows the quality of a downlink measured usingthe downlink data (a reference signal).

The detail will be described in the following. In the followingdescription, a plurality of base stations join the same CoMP grouptransmit a reference signal and downlink data in CoMP transmission.Thus, reference signals from a plurality of base stations arecode-multiplexed and received at a terminal. A base station reports to aterminal in advance information showing a resource (for example, PRB) tobe used to transmit a CQI signal.

A configuration of base station 300 according to the present embodimentis shown in FIG. 12, and a configuration of terminal 400 according tothe present embodiment is shown in FIG. 13. Parts in FIG. 12 that arethe same as in FIG. 9 (Embodiment 1) will be assigned the same referencenumerals as in FIG. 9 and overlapping descriptions will be omitted. Inthe same way, parts in FIG. 13 that are the same as in FIG. 10(Embodiment 1) will be assigned the same reference numerals as in FIG.10 and overlapping descriptions will be omitted. As described above, aCQI signal is not subject to second spreading using an orthogonal codesequence (a Walsh sequence or a Fourier sequence), so that, in basestation 300 shown in FIG. 12 despreading section 114 shown in FIG. 9becomes unnecessary and in terminal 400 shown in FIG. 13 spreadingsection 217 becomes unnecessary.

In base station 300 shown in FIG. 12, analog information of the CQIsignals which have been received at other base station joining the sameCoMP group as terminal 300, is input to determination section 118through backhaul from CoMP control section 117. Also, a CQI signalreceived at terminal 300 is input to determination section 118 fromcorrelation processing section 116. Determination section 118synthesizes a CQI signal input from correlation processing section 116and a CQI signal input from CoMP control section 117, and demodulatesthe CQI signal being the synthesized result.

MCS control section 301 controls a MCS (a coding rate and a modulationscheme) based on CQI information of a plurality of base stations,included in a CQI signal input from determination section 118. MCScontrol section 301 outputs a controlled coding rate to coding section105, and outputs a controlled modulation scheme to modulating section107.

Coding section 105 modulates transmitting data according to a codingrate input from MCS control section 301, and modulating section 107modulates a coded transmitting date according to a modulation schemeinput from MCS control section 301.

On the other hand, in terminal 400 shown in FIG. 13, extracting section205 extracts a reference signal transmitted in CoMP transmission from aplurality of base stations joining the same CoMP group (a signal inwhich reference signals from each base station are code-multiplexed) tomeasuring section 401.

Measuring section 401 uses a reference signal input from extractingsection 205 and measures downlink quality between terminal 400 and eachbase station respectively. Here, it is difficult to make CQI informationshowing downlink quality for each of a plurality of base stationsseparately arrive at all base stations joining the CoMP group. Then,measuring section 401 groups CQI information showing downlink qualityfor measured multiple base stations, for example to one CQI signal.Measuring section 401 outputs a CQI signal including CQI information ofa plurality of base stations to modulating section 213.

Control section 209 of terminal 400 according to the present embodimentwill be described in the following.

In the following description, a case will be described using as shown inFIG. 14A, the same eNBs and UEs as eNB 1-eNB 5 and UE 1-UE 3 shown inFIG. 11A. Also, eNB 1-eNB 5 shown in FIG. 14A each have theconfiguration of base station 300 shown in FIG. 12, and UE 1-UE 3 eachhave the configuration of terminal 400 shown in FIG. 13. Also, each UEreceives a reference signal from a plurality of eNBs join the CoMP groupincluding an eNB to which that UE belongs, and transmits a measured CQIsignal by using the reference signal. Thus, in FIG. 14A, UE 1 receivesreference signals from eNB 1-eNB 3 join CoMP group A, UE 2 receivesreference signals from eNB 1-eNB 3 join CoMP group A, and UE 3 receivesreference signals from eNB 1, eNB 4, and eNB 5 join CoMP group B. Inother words, eNB 1-eNB 3 joining CoMP group A transmit reference signalsto UE 1 and UE 2 in CoMP transmission, and eNB 1, eNB 4, and eNB 5joining CoMP group B transmit reference signals to UE 3 in CoMPtransmission.

Also, uplink resources for transmitting a CQI signal (for example, aplurality of PUCCHs shown in FIG. 1) is represented as a plurality ofPRBs (PRBs for a CQI signal), as shown in FIG. 14B. As shown in FIG.14B, similar to embodiment 1, among a plurality of PRBs, some PRBs ofthese PRBs are set on a per CoMP group basis. Also, the special IDs ofCoMP groups are associated with PRBs corresponding to CoMP groups.

For this reason, similar to embodiment 1, if control section 209 of eachUE is reported that a CQI signal which that UE transmits is not receivedin CoMP reception, control section 209 of each UE calculates a spreadsequence and hopping pattern of a CQI signal using the cell ID of an eNBto which that UE belongs.

Also, similar to embodiment 1, if control section 209 of each UE isreported that a CQI signal which that UE transmits is to be received inCoMP reception, control section 209 of each UE calculates a spreadsequence and hopping pattern of a CQI signal using a special ID of theCoMP group an eNB to which that UE belongs joins.

By this means, similar to embodiment 1, CQI signals transmitted from UEsjoining the same COMP group and belonging to mutually different eNBs,are received in CoMP reception orthogonally to each other.

Thus, even if the terminals belong to mutually different base stationcells, it is still possible to code-multiplex CQI signals in the samePRB. Thus, base stations joining the same CoMP group can receive CQIsignals from terminals, which are orthogonal to each other, in CoMPreception.

Therefore, according to the present embodiment, CQI signals to bereceived in CoMP reception at a plurality of base stations are spreadusing a hopping pattern which is common between a plurality of basestations joining the same CoMP group. Thus, each terminal can make a CQIsignal to be received in CoMP reception in the same CoMP group, beorthogonal to each other, and be code-multiplexed with time andfrequency resources (PRBs) used as an uplink control channel. For thisreason, a CQI signal transmitted from each terminal are orthogonal toeach other and does not interfere with each other, so that each basestation can effectively receive the CQI signal from each terminal inCoMP reception. Thus, according to this embodiment, even if a CQI signalis to be received in CoMP reception, the same advantage result can beachieved as embodiment 1. By this means, in a base station, CoMPreception improves the receiving quality of a CQI signal, so that thethroughput of downlink CoMP transmission can be improved using moreaccurate CQI information.

(Embodiment 3)

Assuming that slot synchronization is established between multiple basestations joining the same CoMP group cases have been described withembodiment 1 and embodiment 2 where slot numbers match between all thebase stations joining the same CoMP group. By contrast with this, a casewhere slot synchronization is not established between multiple basestations joining the same CoMP group—that is, a case where slot numbersdo not match between all the base stations joining the same CoMPgroup—will be described with the present embodiment.

Here, a hopping pattern of a control signal (a response signal or a CQIsignal) is defined by cyclic shifting for each slot a resourcearrangement of a control channel (PUCCH) for a control signal on acyclic shift axis. Then, a base station and a terminal according to thepresent embodiment adjust a hopping pattern showing correspondencebetween a resource arrangement and slot numbers of multiple controlchannels on a cyclic shift axis, using the difference between slotnumbers of multiple base stations.

The detail will be described in the following. As embodiment 1 andembodiment 2, a base station according to the present embodiment reportsto a terminal, the cell ID of the base station, time and frequencyresources (for example, PRBs) to transmit a control signal (a responsesignal or a CQI signal), and a special ID associated with the CoMP groupwhich the base station joins. In addition to the above, a base stationaccording to the present embodiment reports the difference between theslot number of a specific base station (for example, a serving eNB of acertain terminal) between multiple base stations including the basestation which join a CoMP group, and the slot number of the basestation, as a tentative slot number (hereinafter referred to as “specialslot number”). That is, based on the slot number at a specific basestation, a plurality of base stations joining a CoMP group calculatesthe difference between the basic slot number and the slot number of eachbase station as a special slot number. Then, each base station reports aspecial slot number for the terminal belonging to the base station.

If a control signal (a response signal or a CQI signal) which theterminal according to the present embodiment (for example, controlsection 209 shown in FIG. 10 and FIG. 13) transmits is to be received inCoMP reception, the terminal calculates a spread sequence and hoppingpattern using the reported special ID of the CoMP group, the slot numberand special slot number of the base station to which the terminalbelongs. Specifically, as embodiment 1 and embodiment 2, a terminalcalculates a spread sequence and hopping pattern of a control signalusing a special ID. Here, to have the same resource arrangement of theslot number of the basic base station, a terminal shifts the slot numberof the base station to which the terminal belongs, through a reportedspecial slot number (that is, apply a shift to match the differencebetween the slot number in the reference base station and the slotnumber of the base station to which the terminal belongs) and uses thehopping pattern of the slot number found there. Therefore, a terminaladjusts the calculated hopping pattern.

By this means, all cells joining a CoMP group can perform CoMPcommunication using the same hopping pattern as the hopping pattern atthe slot number of the base station which becomes the basic.

Thus, according to the present embodiment, even if a slotsynchronization between multiple base stations joining CoMP group is notestablished, the same result can be acquired as embodiment 1 andembodiment 2.

The embodiments of the present invention have been explained in theabove.

Cases have been described with the above embodiments where a responsesignal (ACK/NACK) or a CQI signal is received in an uplink in CoMPreception. However, in the present invention, a signal to be received asa CoMP reception is not limited to a CQI signal and a response signal.The present invention is equally applicable to, for example, RI (RankIndicator) showing the number of Rank in a downlink channel matrix, orSR (Scheduling Request) to report a base station that transmitting datais generated on a terminal side.

Cases have been described with the above embodiments where a special IDis set as a unique parameter associated with a CoMP PRB. However, in thepresent invention, as a unique parameter associated with a CoMP PRB, forexample, a unique power control parameter can be set in addition to thespecial ID. Thus, a base station can report for a terminal the specialID and the power control parameter associated with a CoMP PRB.

Also, the PUCCH used in the above embodiments is a channel to feed backa response signal (ACK or NACK), so that is referred as an ACK/NACKchannel.

A terminal may be referred to as a terminal station, UE, MT, MS, and STA(Station). A base station may be referred to as Node B, BS, and AP. Asubcarrier may be referred to as a tone. A CP may be referred to as aguard interval (GI).

The method of error detection is not limited to a CRC check.

The method of exchanging between a frequency domain and a time domain isnot limited to an IFFT and a FFT.

Embodiments mentioned above explain examples when the present inventionis performed by hardware, but the present invention can be implementedwith software.

Furthermore, each function block employed in the description of each ofthe aforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells in an LSI can be regenerated is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2008-314791, filed onDec. 10, 2008, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The present invention can be applied to such as a mobile communicationsystem.

The invention claimed is:
 1. A radio communication terminal apparatuscomprising: circuitry, which, in operation, (i) first-spreads a responsesignal using a first sequence defined by one of a plurality of cyclicshifts, wherein said one of the plurality of cyclic shifts variesbetween symbols according to a cyclic shift hopping pattern set based ona second identity, which is different from a first identity specific toa cell and which is set independently of the first identity, and (ii)second-spreads the response signal, which is first-spread, using one ofa plurality of second sequences that are orthogonal to each other; and atransmitter, which, in operation, transmits the response signal.
 2. Theradio communication terminal apparatus according to claim 1, wherein thecyclic shift hopping pattern is common between a plurality of basestations communicating with the radio communication terminal apparatus.3. The radio communication terminal apparatus according to claim 1,wherein, using a difference between slot numbers in a plurality of basestations communicating with the radio communication terminal apparatus,the cyclic shift hopping pattern is adjusted.
 4. The radio communicationterminal apparatus according to claim 3, wherein, the cyclic shifthopping pattern is adjusted using a difference between a slot number ina base station, to which the radio communication terminal apparatusbelongs, and a slot number in a specific base station apparatus among aplurality of base stations communicating with the radio communicationterminal apparatus.
 5. The radio communication terminal apparatusaccording to claim 1, wherein the second identity is common between aplurality of base stations communicating with the radio communicationterminal apparatus.
 6. The radio communication terminal apparatusaccording to claim 1, wherein the cyclic shift hopping pattern is setbased on one of the first identity and the second identity according toa signaling from a base station communicating with the radiocommunication terminal apparatus.
 7. The radio communication terminalapparatus according to claim 1, wherein a number of bits in the firstidentity is same as that in the second identity.
 8. The radiocommunication terminal apparatus according to claim 1, wherein thesecond identity is not related to a parameter of a downlink.
 9. Theradio communication terminal apparatus according to claim 1, wherein thesecond identity is related to a resource used for transmission of theresponse signal.
 10. A signal spreading method at a terminal, the methodcomprising: first-spreading a response signal using a first sequencedefined by one of a plurality of cyclic shifts, wherein said one of theplurality of cyclic shifts varies between symbols according to a cyclicshift hopping pattern set based on a second identity, which is differentfrom a first identity specific to a cell and which is set independentlyof the first identity; second-spreading the response signal, which isfirst-spread, using one of a plurality of second sequences that areorthogonal to each other; and transmitting the response signal.